You Do Need power plug adapter while traveling from Saint Martin to Cuba.

Here is Why You Need An Adapter

The outlet and plug type used in Cuba are A, B, C and L and in Saint Martin are C and E. This is how they look like.

Saint Martin

In Saint Martin, outlets of type C and E are in use.

Type C

Type E

Cuba

In Cuba, outlets of type A, B, C and L are in use.

Type A

Type B

Type C

Type L